Non-invasive respiratory ventilation and pressure support therapies involve the placement of a user interface device, which is typically a nasal or nasal/oral mask, on the face of a user, such as a patient, to interface the respiratory ventilation or pressure support system with the airway of the patient so that a flow of breathing gas can be delivered from the pressure/flow generating device to the airway of the patient.
In recent years, continuous positive air pressure (CPAP) therapy, a method of respiratory ventilation, has become a common treatment for individuals suffering from sleep disorders such as obstructive sleep apnea (OSA) or other breathing ailments. The positive pressure air may be delivered to the patient's upper airway to prevent the upper airway tissues from collapsing during sleep, thus reducing the occurrence and/or severity of sleep apnea. A user interface device, such as nasal or nasal/oral mask, is typically used to deliver continuous positive air pressure (CPAP) to the user.
Such a user interface device must have an effective seal, needs to be held on securely, and may be worn by the user, such as a patient, over extended periods of time, for example, during the night while sleeping or during the day when working in an emergency situation. Therefore, the user interface device should be as comfortable as possible. Otherwise the patient may avoid wearing the interface device. This can defeat the purpose of the pressure support therapy or expose the wearer to dangers from toxins for example. It is also important that the user interface device provides a tight enough seal against a patient's face without discomfort. A problem arises in that in order for the mask to maintain a seal without any undue gas leaks around the periphery of the mask, the mask cushion may be compressed against the patient's face. This is most notable, for example, in masks having a bubble type cushion. While the bubble cushion itself is comfortable, it does not provide adequate support, which may cause gas leaks around the periphery of the mask. The bubble effect is diminished when the headgear strap force is increased to improve stability.
An additional disadvantage of conventional user interface devices is, for example, that conventional masks may form a poor seal with the face of a patient, because many mask assemblies conform to only standard sizes and shapes. For example, conventional masks may not account for differences in the sizes or shapes of the facial features of different patients, thus causing discomfort or pain. Still further, because of the poor seals or fits often associated with conventional masks, the mask may not stay in place, and may shift or move, while in use and may fail to adequately prevent leakage. Accordingly, such user interface devices or masks should be made soft enough to adapt to different face geometries, should stay on compliant under pulling of the hose aside, should be rigid enough to hold the mask on the same place on the face during use, and should not leak under the working air pressure.
In severe cases, patients wearing a typical face mask as well known in the art may develop skin irritation or even wounds from wearing the mask. One reason for this is that pressure points may develop while wearing the mask. As there are many differences between human faces, it is very difficult to develop a limited number of masks that should fit everyone. For optimal comfort, a mask should ideally be customized to fit its user's face, but currently, involved costs prohibit this.
A prior art approach to conform the periphery of a mask cushion to the contours of a user's face is to include a pliable wire into or adjacent to the cushion, as disclosed, for example, in U.S. Pat. No. 7,958,893 B2. It is relatively difficult to adjust a wire to the contours of a face by bending the wire. Furthermore, the wire may not capable of holding a certain form over long periods of time, especially with mechanical impact to the wire, for example, during the movements of a user while sleeping. Unintended bending of the wire may then lead again to undesired pressure points. Still further, prolonged bending of such a wire may lead to damage or breakage of the wire, which would make a mask cushion containing the wire unusable.